A file for reading and writing DBPF files
DBPF(fd): takes a file and parses the first 96 bytes, checking to make sure it is a DBPF. if fd is a string, try and open(fd, 'rb') parse the index into self.records try to parse the directory record into self.records, setting the record.size field to the un
DBPF.records: retrieves the entirity of the index table from the file
DBPF.search(tgi): retreive a number of records that match the passed type/group/instance ID's